The invention relates to a lubricating device for lubricating at least one sliding face portion of a telescopic shaft. The telescopic shaft has two profiled tubes which are inserted into one another. The tubes transmit torque and are displaceable relative to one another along a longitudinal axis. An inner profiled tube is positioned inside an outer profiled tube. A lubricating element is associated with the inner profiled tube. The lubricating element passes lubricant to the sliding face portion of the tubes to be lubricated. The invention also relates to a telescopic shaft having such a lubricating device.
A lubricating device is described in DE 42 37 176 CL published Jun. 1, 1994. The lubricating device has a first formed piece inserted into the end of an inner profiled tube. The inserted end is remote from the joint yoke of a driveshaft provided with universal joints. The two ends of the formed piece extend substantially transversely to the longitudinal axis of the profiled tube. The ends are arranged in radially extending bores of the inner profiled tube. The first formed piece has a through-bore which is open towards the above-mentioned bores in the inner profiled tube. The bores in the inner profiled tube are positioned opposite the carrying surface portions of the outer profiled tube. Thus, the carrying surface portions of the inner and outer profiled tubes, which slide on one another and participate in the transmission of torque are, from time to time, supplied with lubricant during the lubricating process. A second profiled piece is inserted into the profiled tube end facing the yoke. An associated lubricating nipple and a hose connect to the second profiled piece to lubricate the tubes. Lubrication is effected periodically by the user. The disadvantage of this system is that re-lubrication can be forgotten or that the quantity of lubricant applied is larger than required for the prevailing conditions.
DE-PS 918 007, published Aug. 5, 1954, describes a lubrication circulation system for propeller shafts of motor vehicles. A filling chamber and a buffer chamber are connected to one another by a return valve. Thus, during operation, oil may move from the filling chamber through splines into the buffer chamber. In turn, the oil may move from the buffer chamber through the return valve, into the filling chamber. The movement of the oil is said to be favorably affected by the normally inclined position of the propeller shaft in the motor vehicle.
DE-GM 19 92 804, published Aug. 29, 1968, describes an automaticlubricating device for propeller shafts. A volume of lubricant is stored between the end of a toothed journal positioned in a toothed sleeve and a cover arranged in the sleeve. The volume of lubricant can be topped up with lubricant by means of a lubricating nipple arranged in the sliding sleeve. A bore is centered on the longitudinal axis of the sliding journal from the end face of the sliding journal pointing towards the chamber. The bore communicates with bores extending radially from the longitudinal axis and ending in the outer face of the sliding journal. In the course of the resulting pumping movement, when the chamber receiving the lubricant is reduced in size, the lubricant moves through the bores into the region between the toothings of the sliding sleeve and sliding journal for the purpose of lubricating same.
The disadvantage of the above embodiments where lubrication is effected through reducing the size of the lubricant storage chamber between the parts participating in the sliding movement, the sliding journal and the sliding sleeve, is that the pumping movement builds up an increased pressure which increases the load on the bearings of the joints. These lubricating devices are not suitable for use in driveshafts for agricultural machinery. This machinery is subject to long stoppage or down times due to the seasonal use of the implements. Furthermore, larger clearances are provided between the sliding profiles in agricultural equipment than in the case of propeller shafts used for driving motor vehicles or used for other engineering purposes.